Mucosal health and microbiota during sea lice parasitism: effect of oral delivery of immunomodulants

鱼类的粘膜表面（皮肤、肠道和鳃）不断与各种各样的病原体相互作用，并与常驻的粘膜微生物群协同作用，是宿主防御的第一道防线。鱼类黏液中有几种免疫因子，它们的存在和丰度会受到病原体感染的影响。因此，粘膜相关的微生物群可能受到影响，这可能导致生态失调，即体内或体内的微生物失衡，从而降低微生物群对先天免疫系统的有益作用，并可能导致机会微生物的继发感染。海虱（Lepeophtheirus salmonis和Caligus spp.）感染是世界范围内海洋养殖鲑鱼最重要的经济病原体。rogercresseyi是影响智利鲑鱼产业的主要体外寄生虫，每年造成的损失估计高达1.2亿美元。这种寄生虫破坏被皮的外表面，为继发性感染病原体提供入口，受感染的鱼也会受到压力，导致免疫抑制，从而增加对继发性感染的易感性。其他Caligus寄生虫（Caligus rogercresseyi和其他Caligus spp）对世界发展中国家和发达地区的海水养殖活动都有不利影响，每年造成1亿美元的经济损失。因此，开发预防或减少海虱感染的新方法是该行业的当务之急。改善治疗策略的必要前提是更好地了解表皮界面上宿主-微生物-寄生虫之间的关系。因此，本研究计划的目的是评估海虱寄生对粘膜健康的影响，包括免疫反应和宿主微生物群的各个方面。我们将通过测定表皮粘液蛋白质组反应、微生物群变化和粘膜转录组变化来评估免疫调节剂对海虱感染易感性以及肠道和粘液质量的影响。我们将在寄生的早期阶段将宿主和海虱的反应联系起来，以便制定新的策略（即确定疫苗抗原、RNAi靶点、益生菌、益生元、免疫调节剂）来控制海冰。

The mucosal surfaces (skin, intestine and gills) of fish are constantly interacting with a wide range of pathogens and, in concert with the resident mucosal microbiota, are the first line of host defence. Several immune factors have been described in fish mucus and their presence and abundance can be affected by pathogen infection. As a consequence, the mucosa-associated microbiota can be affected and this may lead to dysbiosis, a microbial imbalance on or inside the body, which reduces the beneficial role of microbiota on the innate immune system and may lead to secondary infections by opportunistic microbes. Sea lice (Lepeophtheirus salmonis and Caligus spp.) infections are the most economically important causative agents of disease in marine-farmed salmonids worldwide. Caligus rogercresseyi is the main ectoparasite affecting the Chilean salmon industry with estimated costs of up to $120 million annually. This parasite damages external surfaces of the integument providing portal of entry for secondary infectious pathogens, and infected fish also become stressed which leads to immunosuppression with consequent increased susceptibility to the secondary infections. Other Caligid parasites (Caligus rogercresseyi and other Caligus spp.) have detrimental impacts on mariculture operations in both developing and developed parts of the world which causes economic losses of US$ 100's millions annually. The development of novel methods to prevent or reduce sea lice infection is therefore a high priority for the industry. An essential prerequisite for improved treatments strategies is a better understanding of relationship between host-microbiome-parasite at the epidermal interface. Therefore, the aim of this research programme is to evaluate the influence of sea lice parasitism on mucosal health, including aspects of the immune response and host microbiota. We will evaluate the effect of immunomodulants on susceptibility to sea lice infection, and on gut and mucus quality by determining epidermal mucus proteomic responses, microbiota changes and mucosal transcriptomic changes. We will correlate the responses of the host and the sea lice during the early stages of parasitism in order to develop new strategies (i.e. identify antigens for vaccines, targets for RNAi, probiotics, prebiotics, immunomodulants) for sea ice control.